Bioverativ has struck a deal to buy True North Therapeutics. The deal will see the Biogen spinout pay $400 million upfront and up to $425 million in milestones to acquire the rare disease biotech and its clinical-phase treatment for cold agglutinin disease (CAD), TNT009.

If the deal closes as expected in the coming months, Bioverativ will gain its first clinical-stage asset. Bioverativ spun out of Biogen in February with two commercial products, a substantial preclinical program and plans to use its $325 million cash pile to fill in the gap between these extremes. The True North takeover marks the start of that process and, if TNT009 can live up to promising early data, will help Bioverativ realize its vision of expanding beyond hemophilia to develop into a rare blood disorder specialist.

“[The takeover] strengthens our pipeline with a potential first-in-class therapy to treat CAD, a rare blood disorder with a high unmet patient need,” Bioverativ CEO John Cox said in a statement. “People living with CAD currently have no approved treatment options and suffer with a significant disease burden including crippling fatigue, frequent transfusions and an increased risk of life-threatening thrombotic events such as pulmonary embolism and stroke.”